Stable fuel oil compositions



United S e Pew I Development Company, Pittsburgh, Pa., a corporation of Delaware 1 J No Drawing FiledMay a1, 1956, seri Nb. 535,933 7 Claims. c1. 44- -66) This invention relates to stable fuel oil compositions. More particularly, the inventionrelates to stabilization of substantially neutral. mixtures of catalytically-cracked and straight run distillate fuel oils.

.Uncompoundeddistillate fuel oil compositions are often troublesome with regard to sludge deposition during storage at normal atmospheric temperatures. Sludge deposits in distillate fuel oils are objectionable in that such deposits can cause clogging of burner cylinders, screens, nozzle, etc., and thereby lead to improper functioning of the combustion apparatus in which the fuel oil is consumed' Although sludge deposition sometimes occurs in straight run distillate oils, and frequently occurs to a substantial degree'in catalytically cracked fuel oil distillates, sludge deposition in blends of straight run and catalytically cracked fuel oil distillates presents an entirely distinct problem from that encountered with either component oil. While the sludge formed in such blended oils probably contains some sludgeof the type formed by each component oil, the sludge formed in blended fuel oils is of difierent composition and is consistently greatly in excess of the amount that can be accounted for from the known sludging tendencies of the individual component oils.

Within the general class ofmixed catalytically cracked and straight-run fuel oils, which in themselves present a severe sludging problem, it has now been found; that substantially neutral mixtures of catalytically cracked and straight run distillate fuel' oils, that is, mixed dis tillate fuel oils that possess a total acid number of not more than about-0.045, constitute an especially difiicult problem with respect to sludge deposition. Such neutral mixed distillate fuel oils have been found consistently to deposit sludge in excess of the amount deposited by similar mixtures that possess total acid numbers of above 0.045 'Moreover, the response of neutral mixtures of catalytically cracked and straight run distillate, fuel oils to sludgeinhibitors that are eifective in blended distillate fuel oils that have total acid numbers above 0.045 is of-tenerratic'. As a matter of fact, is not an extraordinary occurrence for sludge inhibitors that are normally effective in blended distillate fuel oils that have total acid. numbersnof above 0.045 to promote sludge deposition in substantially neutral blended distillate fuel oils.

The present invention relates .to stable, compounded fuel oil compositions Comprising mixed catalytically cracked and straight run distillate fuel oils. These compdsitionspossess good appearance, exhibit improved stability with respect to sludge deposition, and are adapted for eifective use as'fuel oils even after being stored for extended periods. We have found that such improved, mixed fuel oil compositions can be obtained by incorporating ina mixture of catalytically cracked and straight run distillate fuel oils that is substantially neutral prior to compounding and that normally tends to deposit ice.

tion of (a) an oil-soluble monocarboxylic .aeid contain= ing at least 8 carbon .atoms permolecule, and (b) a normalalkaline earth metal salt of an alkylbenzene sulfonic acid containing 1 to 3 alkyl substituents per mole cule, at least one of which alkyl substituents contains 12 to 30 carbon atoms. The normal alkaline earth metal alkylbenzene sulfonate and the oil-soluble monocarboxylic acid can be employed in varying proportions with respect to oneanother. It is generally preferred to add them in weight proportions of about 1:1 to about 1:2, but other proportions can be used, provided that each compound is present in an amount corresponding to at least about 0.01 percent by Weight of the composi tion. Usually the compounds will be employedin weight ratios varying from 1:5 to 551. V k

The exact manner of functioning of the herein disclosed combinations of carboxylic acids and sulfonates has not been definitely determined, and accordingly, the invention is not limited to any particular theory of operation. It may be that such combinations inhibit deposition of sludge by preventing formation of sludge or sludge precursors. Alternatively, it may be that the herein disclosed combinations oftarboxylic acids and sulfonates function as solubilizing agents for the sludge. However, regardless of the particular mechanism bywhich the herein disclosed combinations'function, it is clear that the components of the"combination 'coact in a unique manner to provide substantially reduced sludge deposition. 7

"Carboxylic acids that are suitable for use in the herein disclosed combinations are oil-soluble monocarboxylic acids that contain at least 8 carbon atoms per molecule. The use of the acids as such is important to minimize emulsificationjash' on combustion, and water leaching. By way of example, good results have been obtained with oil-soluble petroleum naphthenic acids. As is known, oil-soluble petroleum naphthenic acids consist principally of mixed alicy'clic monocarboxylic acids containing -8 or more carbon atoms per molecule, andare recovered by alkali washing of petroleum distillates such as kerosene, naphtha, gas oil and lubricating distillates and by subsequent acidification of the naphthenic acid salts thus obtained. Such acid mixtures normally possess average molecular weights "ranging from about 200 to about 450. Although oil-soluble naphthenic acids derived-from petroleum are preferred, the invention also includes the use of oil-soluble synthetic naphthenic acids. Examples of such acids are'cyclohexyl acetic, cyclohexyl prop-ionic and cyclohexyl stearic acids. 7

The invention is not limited to oil-soluble petroleum naphthenic acids, as, in fact, especially effective results have been obtained with combinations of normal alkaline earth metal sulfonates of the class disclosed herein and oil-soluble open-chain or acyclic, aliphatic monocarboxyli c acids containing 8 or more carbon atoms'per molecule. Specific examples of preferred acids within this class are 2-ethylhexoic acid, oleic acid aud stearic acid; Examples of other acids within this class are capyrylic, myristic, lauric,'eicosanoic and triacontanoic acids, Mixtures of long chain fatty acids such as can be obtained from the saponification'of natural fats and oils are also suitable. Examples of such acids are coconut, soy, tallow and tall oil fatty acids. In the case of such mixtures, the long chain fatty acids will contain 8 to 20 carbon atoms per molecule.

Sulfonates that aresuitable for use in the herein disclosed combinations are the normal alkaline earth metal salts of alkylbenzene sulfonic acids that contain 1 to 3 ,alkyl groups per molecule, at least one of said alkyl groups containing at least 12 carbon'atoms in the chain and preferably from 12 to 30 carbon atoms. The use of 9 a the normal alkaline earth metal salts is important to avoid interreaction with the acidic component of the herein disclosed combinations. Normal barium salts of monoalkylbenzene sulfonic acids whose alkyl groups contain 12to 24 carbon'atoms in the chain are especially effective for the purposes of this invention.

In other words, the class of sulfonates that are suitable for the purposes of the present invention can be represented by the following generic formula:

SOs- R1 Mei-iwhere Me is an alkaline earth metal, R is an alkyl group containing at least 12 carbon atoms, preferably 12 to 30 and more preferably 12 to 24 carbon atoms in the chain, and R and R are'hydrogen or alkyl groups which may or may not be of the same kind as R For example, R and R can be dodecyl, hexadecyl, tetracosyl, methyl, ethyl or the like. It is an important effect of the relatively long chain alkyl substituent or substituents of the sulfonic acid nucleus to impart oil-solubility to the ultimate compounds, and the position of the substituents on the aromatic nucleus is not important from this standpoint.

Examples of sulfonates, the use of which is included by this invention, are the normal barium, calcium and strontium salts of dodecyl-, didodecyl-, eicosyl-, triacontanyl-, wax alkyland kerosene alkylbenzene sulfonic acids. Examples of other materials which can be used are the calcium, barium and strontium salts of the dodecyl-, octadecyland wax alkyltoluene sulfonic acids. Other materials that can be used in the compositions of this invention are the normal barium, calcium and strontium salts of oil-soluble polyethylated, polypropylated, polybutylated and polyisobutylated benzene and toluene sulfonic acids.

The addition of the herein disclosed combinations of compounds to mixed distillate fuel oils in small amounts has been found to produce good results. Thus, satisfactory results are obtained when using between about 0.02 to about 0.6 percent of the combination by weight of the mixed fuel oil composition. However, best results are ordinarily obtained when using about 0.05 to about 0.1 percent of the combination by weight of the mixed fuel oil composition. While I prefer to employ the carboxylic acid and sulfonate in weight proportions of about 1:1 to about 1:2, good results will nevertheless also be obtained when using proportions of about 1:5 to 5:1 provided that each component is present in an amount of at least 0.01 weight percent.. The most desirable proportions of the herein described combinations will vary somewhat with the individual fuel oil, but in every case the combination of carboxylic acid and sulfonate should be employed in an amount sufficient to provide a total acid number in the mixed fuel oil composition of about 0.05 or greater. Normally, it is prefereable to employ the combination in an amount sufiicient to raise the total acid number of the fuel oil to about 0.1. Greater proportions can be used, but with little additional advantage. Ordinarily the use of the combination of carboxylic acid and sulfonate in proportions such that the carboxylic acid constitutes about 0.01 to about 0.05 percent by weight of the fuel oil composition will raise the total acid number of the fuel oil composition to the desired degree and will produce good sludge inhibition. However, the combination of carboxylic acid and sulfonate can also be used in proportions such that the carboxylic acid will constitute a higher percentage of the fuel oil composition, for example as high as 0.5 percent of the composition. The amount of sulfonate present in the fuel oil composition will normally vary between about 0.01 and about 0.05

weight percent when the combination is employed in the fuel oil composition in proportions such as to provide a carboxylic acid concentration of 0.01 to 0.05, and between 0.01 and 0.1 when the combination is employed in proportions such as to provide a carboxylic acid concentration of 0.01 to 0.5.

The herein disclosed compounds may be incorporated in the mixed fuel oil in any suitable manner. For example, they may be added either separately or together to either or both of the catalytically cracked or straight run distillate fuel oils prior to mixing the two, or they may be added to the mixed oils. Where the compounds are incorporated in the mixed oil, it is unnecessary to do this immediately after mixing the oils. However, it will usually be preferable to add the compounds prior to any appreciable deposition of sludge from the mixed oils. The compounds can be added as such, but it is normally preferred to employ them in the form of a concentrated solution or concentrated solutions in an oil carrier. After addition, some circulation of the mixed oil will normally be desirable to expedite formation of a uniform composition, but this is not absolutely necessary.

The problem with which the present invention is concerned exists only with substantially neutral mixtures of catalytically cracked and straight run distillate fuel oils, that is mixed oils that possess a total acid number (ASTM D 974) of not more than 0.045. Such oils are obtained by the blending of component distillate oils that individually have low total acid numbers .in proportions such as to produce a low total acid number in the blend. Such oils are also obtained by treating individual distillate oils or blended distillate oils that have a higher total acid number with aqueous alkali and water washing. Aqueous alkali is conventionally employed, as such, or with solutizers or other matenials, for example, such as sodium isobutyrate, or litharge and elemental sulfur in the form of doctor solution, to sweeten sour distillates, that is, to remove mercaptans, phenols and thiophenols and/or to convert mercaptans to disulfides.

The compositions of this invention can be further illustrated by reference to the following specific embodiments.

EXAMPLE I A stable mixed distillate fuel oil having improved sludging characteristics is prepared in accordance with this inventionby incorporating a combination of petroleum naphthenic acids and a normal barium alkylbenzene sulfonate in a blended No. 2 fuel oil (Blend A) having a total acid number of 0.008 before compounding. The fuel oil blend is composed of a 1:1:1 volume ratio mixture of catalytically cracked No. 2 fuel oil distillate, South Louisiana straight run fuel oil distillate and doctor sweetened West Texas straight run No. 2 fuel oil distillate, which mixture had been pretreated with 0.06 weight percent sodium hydroxide and water washed.

The barium alkylbenzene sulfonate in this example is a commercial product comprising a 50 percent mineral oil solution of the normal barium salts of mixed monoalkylbenzene sulfonic acids having an average of 17 alkyl carbon atoms per molecule, a typical sample of which concentrate had the following inspections:

Gravity, API, 60 F. 17.9 Viscosity (cs):

F. 45.41 210 F. 7.39 Pour point, F. 20 Flash point, F. 405 Neutralization value (ASTM D 974) total acid number 0.06 Percent S (bomb) 1.37 Percent ash (sulfate) 8.46

The naphthenic acids employed in the fuel oil composition of this example consist of a distillate fraction having a boiling range of -185 C. at 3 mm. Hg

pressureflwhich distillate fraction is obtained by redistillation of commercial petroleum naphthenic acids, pre-i pared in conventional manner from petroleum distillates, a typical sample of which commercial acids had the fol- The make-up of the fuel oil ample is as follows:

Make-up, percent by vol.:

composition of this ex- Fuel oil blend A "99.939 Barium alkylbenzene sulfonate (50% cone.) 7 0.020 Naphthenic acids s 0.041"

. EXAMPLE 11..

reduced sludging potential is prepared in accordance with this invention by incorporating a combination of the petroleum naphthenic acids of Example I and the barium alkylbenzene sulfonate of Example I in a blended No. 21 fuel oil (Blend B), composed of 47.5 volume percent, catalytically cracked No. 2 fuel oil distillate, 31.3 volume percent doctorsweetened West Texas straight'run No. 2

fuel oil distillate, and 21.3 volume percent virgin Coastal straight run No. 2 fuel oil distillate, and having a total acid number of 0.01 prior to compounding. The makeup of the compounded fuel oil of this example is as follows:

Make-up, percent by vol.:

Fuel oil blend B -1 99.935 Barium alkylbenzene sulfonate (50% conc.) Naphthenic acids EXAMPLE III Make-up, percent by vol.:

Fuel oil blend B 99.955 Calcium dodecylbenzene sulfo- 0.020 (active comnate. ponent). Naphthenic acids 1 0.025. 7

EXAMPLE IV Other improved compounded fuel oil blends are prepared according tothis invention by incorporation of a combination of thenaphthenic acids of Example I and the barium alkylbenzene sulfonate of Example I- in a blended No. 2 fuel oil (Blend C) having the same makeup as Blend B of Example II, but having a total acid number of 0.03 prior to compounding. The make-up' of the compounded fuel oils-of this example is as follows;

Make-up, Percent by Wt: Fuel Oil Blend C-.' 99. 951 99. 931 911 99. 861 99. 761 Barium Alkylbenzene Sulfonate (50% cone.) 0. 039- 0.039 0.039 0.039 0.039 Naphthenlc Acids 0. 01 0.03 0. 05 0.100 0. 200

Another compounded fuel oil composition having a- 6 EXAMPLE V.

Additional compounded distillate fuel oil compositions according to this invention are prepared using the follow- 7 ing proportions of fuel .oil Blend C ofExample IV, the barium alkylbenzene sulfonate of Example I and 2-eth-- ylhexoic acid:

Make-up, Percent by'Wt;

Fuel Oil Blend 0. 99. 951 99. 931 99. 911 99. 861 99. 761 Barium Alkylbenzene Sultanate cone). 0.039 0.039 0.039 0.039 0.039 2-Ethylhexolc Acid 0.010 0. 030 0.050 0.100 0. 200

EXAMPLE VI.

Still further compounded blended distillate fuel oil compositions are prepared using the barium sulfonate of Example I, fuel oil Blend C of Example IV and oleic acid. These compositions are prepared according to the following proportions:

Make-up, Percent by Wt.:

Fuel Oil Blend 0 99. 951 99. 931 99.911 99. 861 99. 761 Barium Alkylbenzene Sulfonate (50% cone.) 0.039 0.039 0.039 0.039 0.039 Oleic Acid 0. 010 0.030 0.050 0.100 0. 200

EXAMPLE VII Still further blended fuel oil compositions according to this invention are prepared using the fuel oil blend of Example IV, the barium alkylbenzene sulfonate of Example I and stearic acid. These compounded fuel oil blends have the following proportions:

Make-up, Percent by Wt.:

Fuel Oil Blend 0 99. 951 99.931 99.911 99. 861 99. 761 Barium Alkylbenzene Sultanate (50% 00110.). 0.039 0.039 0.039 0.039 0.039 Stearic Acid 0.010 0.030 0.050 0.100 0.200

The distinct nature of the sludging problem with mixtures of catalytically cracked and straight run No. 2 fuel oil distillates possessing a total acid number of less than 0.045 before compounding was demonstrated by comparative accelerated sludging tests carried out on an uninhibited ftlel oil blend having a total acid number of 0.1 (Blend A before sodium hydroxide treatment and water Washing), an uninhibited fuel oil blend having a total acid number of 0.01 (fuel oil Blend B) and an uninhibited fuel oil blend having a total acid number of 0.03 (fuel oil Blend C). To further demonstrate the unique 1 nature of the problem with which this invention is con cerned, an uninhibited sample of fuel oil Blend A having a total acid number of 0.008 was also tested. The ac-. celerated sludging test referred to in the description of this invention is carried out by heating 600 gram samples of the fuel oil composition being tested for periods varying from 1-6 to 64 hours at 210 F. in loosely stoppered, one-quart clear glass bottles. Following each heating period each test sample is cooled to room temperature and filtered by suction through tared, medium porosity. fritted glassGooch-type crucibles. The sludge in each crucible is washed with heptane. The respective crucibles are then dried in an oven maintained at 210 F. for one hour, cooled in a desiccator and reweighed... The increase in weight is recorded as millisludge 'produced in inhibited and'injuninhibited samples of the fuel oil.

Using a rough rule-ofthumb based on experience, one hour of storage under the conditions of the accelerated test' is equivalent to about't'en days of storage under actual field conditions. The results of the foregoing tests carried out on uninhibited fuel oils are presented in Table A below.

Table A Test Sample No 1 2 3 4 Makeup, Percent by Vol.2

Fuel Oil Blend A (Before NaOH Treatment) 100 Fuel Oil Blend B 100 Fuel Oil Blend C Fuel Oil Blend A Inspections:

Neutralization Value, Total Acid N0.

(Colorimetric) 0.1 0.01 0.03 0.008 Storage Stability; 210 F Sludge Mg./600 G. Oil:

From the results presented in the foregoing table it is mo 10 moter when used alone.

In order to demonstrate the effects of varying the proportions of the monocarboxylic acids and alkaline earth metal sulfonates in the herein disclosed combinations, the blended fuel oil compositions of Example IV V were subjected to the conditions of the foregoing accelerated test; The results of these tests are presented in Table C below.

Table C Test Run No .1 1 2 3 4 5 6 Make-up, percent: 7

Fuel Oil Blend 0 (Total Acid No. 100

Example IV Compounded Fuel Oils- Compounded Fuel Oil (a) 100 Compounded Fuel Oil (b)- Componnded Fuel Oil (0) Inspections:

Nautralizationvalue, Total AcidNo. 0.03 0.053 o.1 0.14 0.25 -0.48

(Colorimetric) Storage Stability, 210 F.-

SIudIgefiMgJGOO G. Oil:

h Calculated; 0.01% naphthenic acids=0.022 total acid No.

apparent that in every case where the total acid number of the fuel oil blend was less than 0.045 the sludging tendencies of the fuel oil blend were unusually severe as compared with the sludging tendencies of an oil having an acid number above 0.045. The distinct nature of the problem is particularly evident from a comparison of runs 1 and 4 which were carried out on fuel oil blends that were identical, except for sodium hydroxide and water treatment to reduce the acid number of fuel oil test sample No. 4. Comparison of the results obtained in these runs shows that the reduction in the acid number due to sodium hydroxide treatment increased the sludging tendencies of the fuel oil blend by about percent.

In order to demonstrate the improved results obtained when using the herein disclosed combinations of monocarboxylic acids and alkaline earth metal sulfonates in mixed catalytically cracked and straight run distillate fuel oil blends having a total acid number of less than 0.045, blends of the class disclosed and containing various amounts of naphthenic acids and alkylbenzene sulfonates singly and in combinations were subjected to the conditions of the above-described accelerated test. The re sults of these tests are presented in Table B below.

TestRunNo 1 2 3 4 Inspections:

Comparison of the results set forth in the foregoing table indicates that a substantial improvement is obtained over a wide range of proportions and that especially 40 effective results were obtained when using about 0.03 to 45 VII were subjected to the conditions of the abovedescribed accelerated sludging test. Representative results from these tests are set forth in Table D below.

Table D Make-up, Percent:

Fuel Oil Blend C Example V (0) Composition. Example VI (0) Composition Example VII (c) Composition 100 Storage Stability, 210 F.-

Sludge, Mg./600 G. Oil:

16 Hrs Table B Example Example Test Sample No 1 2 3 I Com- 4 5 6 II Composition position Make-up percent by Vol.2

Fuel Oil Blend A (Total Acid No. 0.008) 100 99. 959 99. 98 99. 939 Fuel Oil Blend B (Total Acid No. 0.01) 100 99. 96 l 99.975 99. 935 Barium Alkylbenzene Sulfonate (50% cone.) 0.02 0.02 0. 04 0.040 N aphthenic Acids 0.041 0. 041 0.025 0. 025 Inspection:

Storage Stability, 210 F. Sludge, Mg./600 G. Oil:

16 Hrs. 40. 8 4 1 1 24 Hrs 49. 7 21. l 7.0 5 1 48. 1 37. 6 40 Hrs 98.9 60. 4 109. 1 4 1 88. 3 25 69.4 5 3 64 Hrs 131.9 110.5 56 1 Treated with 0.06% NaOH and water washed before incorporation oi additive.

v-ww duced sludging tendencies.

Comparison of the results obtained in runs 2, 3 and 4 with the results obtained in connection with the uninhibited fuel oil of test run No. 1 shows that excellent results are obtained when using other monocarboxylic acids within the scope of this invention.

Although the combinations of compounds employed in the foregoing tests are preferred for use in the compounded fuel oil compositionsrof the invention, it will be understood that other combinations of monocarboxylic acids and sulfonates of the kind disclosed herein will possess similar properties and that such other combinations can be used to prepare improved fuel oil compositions within the scope of this invention and havingre- In other words, the invention includes the use of other disclosed oil-soluble monocarboxylic acids in combination with other disclosed normal alkaline earth metal sulfonates. For example, lauric acid and normal calcium polypropylated benzene sulfonate can be used.

If desired the stable fuel oil compositions may contain in addition to the compounds previously discussed oxidation inhibitors, corrosion inhibitors, anti-foam agents, ignition quality improvers, combustion improvers and other additives adapted to improve the oil in one or more respects.

No. 2 fuel oils are defined in the ASTM Standards on Petroleum Products and Lubricants published in Noinhibit sludge deposition from said mixture of oils and comprising at least 0.01 percent by weight of the composition of each of said acid and said alkaline earth metal salt of said sulfonic acid and not more than 0.6 percent of said combination by weight of the composition.

2. The compounded fuel oil of claim 1 wherein each of said monocarboxylic acid and said alkaline earth metal salt is present in an amount of 0.01 to 0.05 percent by normally tends to deposit sludge, and containing a small vember 195'4, underdesignation D'396-48T.

It will be apparent to those skilled in the art that many modifications and variations of the herein disclosed invention may be resorted to without departing from the spirit thereof. Accordingly, only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. A compounded fuel oil composition comprising a major amount of a mixture of catalytically cracked and straight run fuel oil distillates that has a total acid number of not more than 0.045 before compounding, and that normally tends to deposit sludge, and containing a small amount of a combination of (a) an open-chain aliphatic monocarboxylic acid containing 8 to 30 carbon atoms per molecule, and (b)' a normal barium salt of an alkylbene sulfonic acid containing 1 to 3 alkyl substituents per molecule, at least one of said alkyl substituents containing 12 to 30 carbon atoms, said small amount being sufficient to inhibit sludge deposition from said mixture of oils and comprising at least 0.01 percent by weight of the composition of each of said acid and said barium salt and not more than 0.6 percent of said combination by weight of the composition.

5. The compounded fuel oil of claim 4 wherein said monocarboxylic acid is 2-ethylhexoic acid.

6. The compounded fuel oil of claim 4 wherein said monocarboxylic acid is oleic acid.

7. The compounded fuel oil of claim 4 wherein said monocarboxylic acid is stearic acid.

References Cited in the file of this patent UNITED STATES PATENTS UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Nos 2,943 924 July 5, 1960 Ira Kukin It is hereby certified that error appears in the-printed specification of the above "numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 10 lines 22 and 23,, for "alkylbene" read alkylbenzene Signed and sealed this 31st. day of January 1961.

(SEAL) Attest:

KARL H AXLINE ROBERT C. WATSON Attesting 0fficer Commissioner of Patents UNITED STATES PATENT OFFICE CEBTEFICATE OF CORRECTIGN Ira Kukin s in the-printed specification or appear hat the said Let-hers It is hereby certified that err ng correction and t of the above "numberedpa'tent requiri Patent should read as corrected below.

Column 10 lines 22 and 23 for "alkylbene" read alkylbenzene e Signed and sealed this 31st day of January 1961a (SEAL) Attest:

ROBERT C. WATSON KAR L AXLINE Commissioner of Patents Attesting Ofiicer 

1. A COMPOUNDED FUEL OIL COMPOSITION COMPRISING A MAJOR AMOUNT OF A MIXTURE OF CATALYTICALLY CRACKED AND STRAIGHT RUN FUEL OIL DISTILLATES THAT HAS A TOTAL ACID NUMBER OF NOT MORE THAN 0.045 BEFORE COMPOUNDING, AND THAT NORMALLY TENDS TO DEPOSIT SLUDGE, AND CONTAINING A SMALL AMOUNT OF A COMBINATION OF (A) AN OIL -SOLUBLE MEMBER SELECTED FROM THE GROUP CONSISTING OF NAPHTHENIC ACIDS CONTAINING AT LEAST 8 CARBON ATOMS AND FATTY ACIDS CONTAINING 8 TO 30 CARBON ATOMS PER MOLECULE, AND (B) A NORMAL ALKALINE EARTH METAL SALT OF AN ALKYLBENZENE SULFONIC ACID CONTAINING 1 TO 3 ALKYL SUBSTITUENTS PER MOLECULE, AT LEAST ONE OF SAID ALKYL SUBSTUENTS CONTAINING 12 TO 30 CARBON ATOMS, SAID SMALL AMOUNT BEING SUFFICIENT TO INHIBIT SLUDGE DEPOSITION FROM SAID MIXTURE OF OILS AND COMPRISING AT LEAST 0.01 PERCENT BY WEIGHT OF THE COMPOSITION OF EACH OF SAID ACID AND SAID ALKALINE EARTH METAL SALT OF SAID SULFONIC ACID AND NOT MORE THAN 0.6 PERCENT OF SAID COMBINATION BY WEIGHT OF THE COMPOSITION. 